U.S. patent application number 12/674121 was filed with the patent office on 2011-05-26 for jet reactor with flow ducts and process for preparing isocyanates using it.
Invention is credited to Jiansheng Ding, Weiqi Hua, Jianfeng Li, Deqiang Ma, Yonghua Shang, Zhongping Sun, Yongsheng Wang, Young Wang.
Application Number | 20110124907 12/674121 |
Document ID | / |
Family ID | 40377803 |
Filed Date | 2011-05-26 |
United States Patent
Application |
20110124907 |
Kind Code |
A1 |
Shang; Yonghua ; et
al. |
May 26, 2011 |
JET REACTOR WITH FLOW DUCTS AND PROCESS FOR PREPARING ISOCYANATES
USING IT
Abstract
The present invention provides a flow duct type jet reactor and
a process for preparing isocyanates using it. The flow duct type
jet reactor situates flow ducts in inner feed pipe which form
whirlpool and reinforce vortex, thereby amine steam rapidly admixes
and reacts with phosgene, and the byproducts are reduced. In
addition, the present process uses a jet-absorption apparatus which
rapidly cools the high temperature gas discharged from the reactor
to a temperature at which the product is thermally stable, and at
the same time provides negative pressure for the reaction process
of the system, and thus saving bulky vacuum system.
Inventors: |
Shang; Yonghua; (Shandong,
CN) ; Sun; Zhongping; (Shandong, CN) ; Li;
Jianfeng; (Shandong, CN) ; Wang; Young;
(Shandong, CN) ; Hua; Weiqi; (Shandong, CN)
; Ma; Deqiang; (Shandong, CN) ; Wang;
Yongsheng; (Shandong, CN) ; Ding; Jiansheng;
(Shandong, CN) |
Family ID: |
40377803 |
Appl. No.: |
12/674121 |
Filed: |
August 21, 2007 |
PCT Filed: |
August 21, 2007 |
PCT NO: |
PCT/CN07/02526 |
371 Date: |
February 18, 2010 |
Current U.S.
Class: |
560/347 ;
422/129 |
Current CPC
Class: |
B01J 2219/00119
20130101; C07C 263/10 20130101; B01J 2219/00252 20130101; C07C
263/10 20130101; B01J 4/002 20130101; B01J 2219/00247 20130101;
B01J 19/26 20130101; C07C 263/10 20130101; C07C 265/14 20130101;
B01J 2219/00254 20130101; B01F 5/0057 20130101; C07C 265/04
20130101 |
Class at
Publication: |
560/347 ;
422/129 |
International
Class: |
C07C 263/10 20060101
C07C263/10; B01J 19/00 20060101 B01J019/00 |
Claims
1. A flow duct type jet reactor, comprising: an internal feed tube,
an external feed tube coaxial with the internal feed tube, and an
annular space defined between two said feed tubes, wherein both
ends of the external feed tube are closed; a reaction tube
coaxially connected to the downstream of the internal feed tube,
jet holes made in the wall of the downstream part of the internal
feed tube and the jet holes are connected with flow ducts.
2. The flow duct type jet reactor according to claim 1, wherein,
said jet holes and said flow ducts are connected in a smooth
transition manner, and the numbers of said jet holes and said flow
ducts connected thereto are 2-20 respectively.
3. The flow duct type jet reactor according to claim 2, wherein,
outlets of flow ducts are positioned at a first suppositional
circle coaxial with the internal feed tube and symmetrically
arranged at the first suppositional circle, and the diameter of
said first suppositional circle is 0.1 to 0.99 times of the inner
diameter of the internal feed tube.
4. The flow duct type jet reactor according to claim 3, wherein,
the flow direction of a feedstock at outlets of flow ducts is
tangent with a second suppositional circle defined by the center of
jet holes, the center of outlets of flow ducts and the axis of the
internal feed tube; flow ducts are engineered to be a curve shape,
and the curve is overlapped with the second suppositional
circle.
5. The flow duct type jet reactor according to claim 4, wherein,
the total cross sectional area of all of jet holes or flow ducts is
2-30% of that of the internal feed tube; said jet holes are
arranged as close as possible to the bottom of the annular space
defined by the internal feed tube and the external feed tube.
6. The flow duct type jet reactor according to claim 5, wherein,
all or parts of said jet holes are arranged on the same cross
section of the internal feed tube, and symmetrically arranged in
the wall of the internal feed tube; said jet holes are positioned
not more than 10 cm away from the bottom of the annular space;
outlets of said flow ducts are positioned on the same cross section
of the internal feed tube.
7. The flow duct type jet reactor according to claim 6, wherein, a
divergent channel is arranged at the downstream of said internal
feed tube, and connected with a reaction tube; the inner diameter
of the reaction tube is 1 to 2 times of that of the internal feed
tube; the distance from said jet holes to the starting point of the
divergent channel is 1-15 times of the diameter of the internal
feed tube, and the angle between the divergent channel and the
stream flow direction in the internal feed tube is 10-30
degrees.
8. The flow duct type jet reactor according to claim 7, wherein,
the external feed tube has porous plates, baffle plates, or packing
layers inside.
9. The flow duct type jet reactor according to claim 8, wherein,
the number of flow ducts is 3-10; the diameter of said first
suppositional circle is 0.4 to 0.9 times of the inner diameter of
the internal feed tube; the total cross sectional area of all of
said jet holes or said flow ducts is 5-15% of that of the internal
feed tube; the distance from said jet holes to the starting point
of the divergent channel is 3-6 times of the diameter of the
internal feed tube.
10. A process of a gas phase phosgenation for preparing aliphatic,
alicyclic, or aromatic isocyanates having a general formula of
R(NCO).sub.n by using the flow duct type jet reactor according to
any of claims 1-9, wherein R denotes an aliphatic, alicyclic, or
aromatic hydrocarbon group with carbon atoms of 1 to 15 and n is an
integral number of 1-10, and said process comprises the following
steps: (a) an amine having a general formula of R(NH.sub.2).sub.n
and phosgene are heated respectively to 120.degree. C.-500.degree.
C. to be gasified, wherein R and n are defined as above; (b)
phosgene enters and flows parallelly through the internal feed tube
of the reactor, and the amine vapor enters the external feed tube
via its inlet and then is ejected to the internal feed tube via jet
holes and flow ducts; (c) phosgene and the amine vapor are mixed
and enter the reaction tube to react.
11. The process according to claim 10, wherein, the process further
comprises step (d): the high temperature gas mixture emerging from
the reaction tube is quenched.
12. The process according to claim 11, wherein, in step (d), the
high temperature gas mixture is quenched by a jet-absorption
apparatus comprising a liquid-gas jet absorber, a circulation pump
and an absorption trough.
13. The process according to claim 12, wherein, the average
velocity of said amine vapor through all of jet holes and flow
ducts is 6 to 120 m/s, and the average velocity of phosgene through
the internal feed tube is 3 to 20 m/s; the velocity ratio of the
amine vapor at outlets of flow ducts to phosgene is 1:1 to
10:1.
14. The process according to claim 13, wherein, in step (a), the
amine vapor is diluted with an inert gas or with an inert solvent
vapor; the inert gas is selected from nitrogen or argon; the inert
solvent is selected from toluene, xylene, chlorobenzene,
o-dichlorobenzene or decalin.
15. The process according to claim 14, wherein, during the
phosgenation of step (c), the absolute pressure in feed tubes is
200-3000 mbar, and the outlet pressure of the reaction tube of the
reactor is 150-1500 mbar; the velocity of the amine vapor at
outlets of jet holes is usually 6-120 m/s.
16. The process according to claim 15, wherein, in step (d), the
absorption solution in the absorption trough has a temperature of
130-150.degree. C., and is selected from pure solvents including
toluene, xylene, chlorobenzene or o-dichlorobenzene, or a mixture
of any of the foregoing solvents with 5 wt %-50 wt % of aliphatic,
alicyclic or aromatic isocyanates of R(NCO).sub.n.
17. The process according to claim 16, wherein, in step (d), the
liquid-gas jet absorber is a venturi-like type one, a rotating jet
with long pipes, or a multi-nozzle jet, and the jet absorber is
single stage or multi-stage; a static mixer is set at the outlet of
the jet absorber; the high speed ejection of liquids inside the jet
absorber provides a vacuum of 0 mbar to -700 mbar to the reaction
system.
18. The process according to claim 17, wherein, the isocyanate is
selected from any of the following chemicals:
1,4-butanediisocyanate, 1,6-hexamethylene diisocyanate,
1,4-cyclohexanediisocyanate, isophorone diisocyanate,
dicyclohexylmethane-4,4'-diisocyanate, nonane triisocyanate, or
toluene-2,4-diisocyanate.
19. The process according to claim 17, wherein, the amine having a
general formula of R(NH.sub.2).sub.n is selected from any of the
following chemicals: 1,4-diaminobutane, 1,6-diaminohexane,
1,4-diaminocyclohexane,
1-amino-3,3,5-trimethyl-5-aminomethyl-cyclohexane,
4,4'-diaminodicyclohexylmethane, triamino nonane, a mixture of
2,4-/2,6-toluene diamines with an isomer ratio of 80/20-65/35, or
pure 2,4-toluene diamine.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is related to, and claims priority in, PCT
Application No. PCT/CN2007/002526, filed on Aug. 21, 2007, is
claimed under 35 U.S.C. .sctn.365, the disclosure of which is
incorporated in its entirety by reference herein.
FIELD OF THE INVENTION
[0002] This invention relates to a jet reactor, especially to a
flow duct type jet reactor, as well as to a process for preparing
isocyanates using the reactor.
BACKGROUND OF THE INVENTION
[0003] As early as in 1940's, it has been reported of a gas-phase
phosgenation for preparing isocyanates (Siefken, Annalen 562, 108,
1949). A gas-phase reaction is usually carried out in a tubular
reactor. This phosgenation reaction is a fast process, which
requires fast mixing rate and meanwhile needs to avoid blockage of
the reactor at a high reaction temperature as possible. In the gas
phase phosgenation at a high temperature, amines and isocyanates
are extremely unstable to stay in a relatively long time at
300-500.degree. C., which may cause decompositions like losing
NH.sub.2 or NCO groups and the like. Thus, on one hand, it needs to
strengthen their mixing and reduce their residence time during the
reaction process at a high temperature; on the other hand, it needs
to conduct the reaction under negative pressure, especially for
feedstocks of high boiling points, so as to make amines gasified at
a relatively low temperature; furthermore, the obtained high
temperature gas mixture needs to be quenched to about 140.degree.
C., so as to minimize the loss of products.
[0004] EP 0, 289, 840 discloses a cylindrical reactor without any
moving parts inside. The reaction is carried out with reactant
streams in a turbulent flow state. The gas phase phosgenation of
aliphatic amines is a very fast reaction process determined by the
mixing velocity. However, due to the back-mixing of reactants,
isocyanates may react with amines to form solid by-products
deposited on the surface of the reactor, which obstruct its gas
flow channel.
[0005] U.S. Pat. No. 4,847,408 adopts a reactor where gaseous
reactants are mixed and react under a strong turbulent flow state.
The reactor has an inner diameter of 2.5 mm and a length of 17.5
mm. The stream of amines is rapidly ejected into the reactor via a
nozzle. And HDI is obtained at 400.degree. C. CN 1, 396, 152
improves the reactor described in U.S. Pat. No. 4,847,408 by
converting the cylindrical reactor into a mixer of venturi-like in
shape. This design may reduce back-mixing and the contact of the
gaseous mixture with the inside wall of the reactor.
[0006] U.S. Pat. No. 6,082,891 describes a preparation of
H.sub.6TDI using a microchannel mixer which shows a good result.
However, a disadvantage of the reactor is that polymers produced
and deposited at a high temperature may block the channel for its
small size, and thereby the operation time has to be shortened.
[0007] EP 0, 289, 840 and U.S. Pat. No. 4,847,408 describe a
condensation of products by absorbing them directly in a solvent.
It needs a large solvent container and a big amount of solvents due
to the short heat exchange time. Furthermore, quenching and
absorption of the high temperature gas mixture may use a heat
exchanger. By-products may deposit on surfaces of the heat
exchanger, which impairs the heat transfer and finally leads to a
blockage of the heat exchanger after a long term operation.
[0008] It can be seen from the above comparison that the
phosgenation reaction of amines in the gas phase is a fast reaction
process, which requires a higher mixing rate to avoid the
production of by-products like ureas so as to avoid blockages. The
key to obtain a good reaction result is to use a reactor having
high mixing efficiency so as to reduce the production of solid
by-products. Furthermore, quenching of a high temperature gas
mixture also reduces the production of by-products. Therefore,
there is a need to find an apparatus and a process for preparation
of isocyanates, which provides rapid efficient mixing of reactants
and quenching of the high temperature gas mixture after the
reaction.
BRIEF DESCRIPTION OF THE INVENTION
[0009] The objective of the invention is to provide a flow duct
type jet reactor, which can strengthen effect of turbulent flow and
significantly improve the mixing effect of reactants so as to
achieve the rapid mixing of reactants.
[0010] The flow duct type jet reactor of the invention comprises an
internal feed tube, an external feed tube coaxial with the internal
feed tube, and an annular space defined between the two feed tubes,
wherein both ends of the external feed tube are closed; a reaction
tube coaxially connected to the downstream of the internal feed
tube; jet holes made in the wall of the downstream part of the
internal feed tube and the jet holes are connected with flow
ducts.
[0011] Wherein, said jet holes and said flow ducts are connected in
a smooth transition manner. The outlets of flow ducts are
positioned at a first suppositional circle which is coaxial with
the internal feed tube, and the diameter of said first
suppositional circle is 0.1 to 0.99 times of that of the internal
feed tube, and preferably 0.4 to 0.9 times. The outlets of said
flow ducts are preferably distributed on the same cross section of
the internal feed tube, and more preferably symmetrically arranged
at the first suppositional circle. Streams emerge from outlets of
said flow ducts in a direction which is tangent with a second
suppositional circle defined by the center of jet holes, the center
of outlets of flow ducts and the axis of the internal feed tube,
although deviations of this arrangement are feasible.
[0012] The cross section of jet holes and flow ducts may be in the
shape of a circle, an oval, a square, a rhombus and the like. The
flow ducts may be engineered to be a curve shape, and the curve is
preferably overlapped with the second suppositional circle defined
by the center of jet holes, the center of outlets of flow ducts and
the axis of the internal tube.
[0013] The numbers of jet holes and flow ducts connected thereto
are 2-20 respectively, preferably 3-15, more preferably 3-10, and
most preferably 4-10. The total cross sectional area of all of jet
holes or flow ducts is 2-30% of that of the internal feed tube, and
preferably 5-15%.
[0014] Jet holes are arranged as close as possible to the bottom of
the annular space defined by the internal feed tube and the
external feed tube, and preferably they are not more than 10 cm
away from the bottom.
[0015] A divergent channel is arranged at the downstream of said
internal feed tube, and connected with a reaction tube. The angle
between the wall of the divergent channel and the stream flow
direction in the internal feed tube is 10-30 degrees. The inner
diameter of the reaction tube is 1 to 2 times of that of the
internal feed tube, and preferably 1.1 to 1.5 times.
[0016] All or parts of jet holes are arranged on the same cross
section perpendicular to the stream flow direction in the internal
feed tube, and symmetrically arranged over the wall of the internal
feed tube, although deviations of this arrangement are
feasible.
[0017] The reactor is generally made of steel, glass, alloy or
enameled steel.
[0018] The external feed tube may be engineered with porous plates,
baffle plates, packing layers and the like inside to stabilize
reactant streams.
[0019] Another objective of the invention is to provide a process
of a gas phase phosgenation for preparing isocyanates by using
above described flow duct type jet reactors. More details are given
as follows:
[0020] A process of a gas phase phosgenation for preparing
aliphatic, alicyclic, or aromatic isocyanates having a general
formula of R(NCO).sub.n by using a above described flow duct type
jet reactor, wherein R denotes an aliphatic, alicyclic, or aromatic
hydrocarbon group with carbon atoms of 1 to 15, preferably 3 to 15,
and more preferably 4 to 13; and the hydrocarbon group may contain
heteroatoms such as O or S; and n is an integral number of 1-10,
preferably 1-5, more preferably 2-4 and most preferably 2 or 3;
said process comprises the following steps:
[0021] (a) an amine having a general formula of R(NH.sub.2).sub.n
and phosgene are heated respectively to 120.degree. C.-500.degree.
C. to be gasified, wherein R and n are defined as above;
[0022] (b) phosgene enters and flows parallelly through the
internal feed tube of the reactor, and the amine in vapor form
enters the external feed tube via its inlet and then is ejected to
the internal feed tube via jet holes and flow ducts;
[0023] (c) phosgene and the amine vapor are mixed and enter the
reaction tube to react.
[0024] Wherein, in step (a), the amine may optionally be diluted
with an inert gas or with the vapors of an inert solvent. The inert
gas may be selected from nitrogen or argon gas and the like, and
the inert solvent may be selected from toluene, xylene,
chlorobenzene, o-dichlorobenzene or decalin and the like. In step
(a), the amine and phosgene are usually heated to 120.degree.
C.-500.degree. C. respectively, and preferably 250.degree.
C.-400.degree. C. Based on the mole quantity of amino group,
phosgene usually exceeds 25%-350%, and preferably 50%-250%, and the
use amount of the inert gas or the inert solvent is usually 0.1-2
times of the mole of amino groups, and preferably 0.2-1 times.
[0025] Wherein, in step (b), the average velocity of the amine
vapor through all of jet holes and flow ducts is 6 to 120 m/s, and
the average velocity of phosgene through the phosgene feed tube is
3 to 20 m/s. The ratio of the velocity of the amine vapor at the
outlets of flow ducts to phosgene is 1:1 to 10:1, and preferably
3:1 to 5:1.
[0026] The amines used in the invention are primary amines which
can turn to a gas form without decomposition. Suitable amines are
aliphatic, alicyclic or aromatic mono-amines, diamines, triamines,
tetramines or pentamines and the like having carbon atoms of 1-15,
preferably 3-15, and more preferably 4-13. For example, suitable
aliphatic diamines include 1,4-diaminobutane, 1,6-diaminohexane,
1,4-diaminocyclohexane,
1-amino-3,3,5-trimethyl-5-aminomethyl-cyclohexane (IPDA),
4,4'-diaminodicyclohexylmethane (H.sub.12MDA) and the like.
Suitable aliphatic triamines include
4-(aminomethyl)octane-1,8-diamine, triaminononane and the like.
Preferred amines are 1,6-diaminohexane, IPDA, H.sub.12MDA and
triaminononane. Suitable aromatic amines include 2,4-/2,6-toluene
diamines with an isomer ratio of 80/20 to 65/35, 2,4-toluene
diamines (TDA), diaminobenzene, naphthalenediamine,
2,4'-/4,4'-diamino diphenyl methane and the isomer mixture thereof.
The amine may also be an amine containing heteroatoms, like
2-tetrahydrofurfurylamine.
[0027] The diamine is preferably 4,4'-diaminodicyclohexylmethane,
1-amino-3,3,5-trimethyl-5-aminomethyl-cyclohexane (IPDA), or
1,6-diaminohexane. the triamine is preferably triamino nonane.
[0028] During the phosgenation of step (c), the pressure (absolute
pressure) in feed tubes is preferably 200 to 3000 mbar, and the
outlet pressure of the reaction tube of the reactor is preferably
150 to 1500 mbar. The velocity of phosgene prior to the mixing is
at least 1 m/s, and preferably 3-20 m/s; the velocity of the amine
vapor at the outlets of jet holes is usually 6-120 m/s, and
preferably 20-100 m/s.
[0029] Wherein, the process further comprises step (d): the high
temperature gas mixture emerging from the reaction tube is
quenched.
[0030] In step (d), the high temperature gas mixture is quenched by
a jet-absorption apparatus, which comprises a liquid-gas jet
absorber, a circulation pump, and an absorption trough. An
absorption solution in the absorption trough is pressured by the
circulation pump, and then ejected to the jet absorber via a nozzle
of the liquid-gas jet absorber; the high temperature gas mixture is
rapidly sucked into the jet absorber due to the negative pressure
brought by the high speed flow of the solution, so as to achieve
sufficient mixing of the solution and the gas mixture, and then
quenching. The reaction product in the absorption trough is further
collected and absorbed by a liquid solvent. And then, after
pressured by the circulation pump, one part of the absorption
solution is transmitted to a phosgenation solution post-process
system for solvent removement and purification, and the other part
is combined with supplementing fresh solvent and transmitted to the
jet absorber for quenching and absorption of the high temperature
gas mixture.
[0031] A packing tower is preferred to be set at the top of the jet
absorber, and a part of the absorption solution is transmitted to
the top of the packing tower after pressured by the circulation
pump, so as to further absorb the unabsorbed gas mixture in the jet
absorber. More preferably, the packing tower is connected with a
condenser wherein gas in the packing tower is further condensed by
the condenser (cooling medium is water), and incondensable gas is
transmitted to a HCl and COCl.sub.2 recycle device so as to improve
the post treatment efficiency of the phosgenation solution.
[0032] In step (d), the absorption solution in the absorption
trough has a temperature in a range of 130-150.degree. C., and may
be selected from pure solvents including toluene, xylene,
chlorobenzene or o-dichlorobenzene, or a mixture of any of the
foregoing solvents with 5 wt %-50 wt % of aliphatic, alicyclic or
aromatic isocyanates of R(NCO).sub.n. The temperature of the
absorption solution prior to the ejection to the jet absorber is
80.degree. C.-120.degree. C.
[0033] In step (d), the liquid-gas jet absorber may be a
venturi-like type one, a rotating jet with long pipes, or a
multi-nozzle jet. The jet absorber may be single stage or
multi-stage. A static mixer is preferred to be set at the outlet of
the jet absorber. Approaches to improve the absorption effect of
the jet absorber are not limited to the set forth ones.
[0034] Wherein, the high speed ejection of the solution inside the
jet absorber may provide a vacuum of 0 mbar to -700 mbar to the
reaction system, and preferably -200 mbar to -500 mbar. The vacuum
is produced by controlling the velocity and the pressure head of
the circulation pump. According to the reaction gas flow rate, the
flow rate in the circulation pump is 20 liters/s-1000 liters/s, and
the gauge pressure of the circulation pump is preferred to be 3
bars to 30 bars.
[0035] The isocyanates of the invention may be selected from any of
the following compounds: 1,4-butanediisocyanate, 1,6-hexamethylene
diisocyanate, 1,4-cyclohexanediisocyanate, isophorone diisocyanate
(IPDI), dicyclohexylmethane-4,4'-diisocyanate (H.sub.12MDI), nonane
triisocyanate, or toluene-2,4-diisocyanate (TDI).
[0036] The advantages of setting certain number of flow ducts at
suitable positions in the internal feed tube are to achieve the
mixing of two components at any position, and to form whirls under
the direction effect and reinforce vortex, so as to ensure the
amine vapor and phosgene are rapidly mixed and react and to
minimize the production of by-products. Besides, the jet absorber
used in the invention quenches the high temperature gas mixture
emerging from the reaction tube to a temperature at which products
are stable, and meanwhile produces negative pressure for the
reaction system. The phosgenation product flows to the jet absorber
fast under negative pressure so as to ensure the phosgenation
product is absorbed, and quenched fast and efficiently. The gas
jet-absorption apparatus used in the invention has a relatively
larger volume flow ratio of liquid-gas, stronger absorption
intensity and more powerful process ability and provides negative
pressure to the reaction tube which is more suitable for the
phosgenation under negative pressure, so as to save bulky vacuum
system and avoid decomposition of amines.
BRIEF DESCRIPTION OF THE FIGURES
[0037] FIG. 1 shows a longitudinal section view through one
embodiment of the flow duct type jet reactor of the invention;
[0038] FIG. 2 is an enlarged view of the cross section along line
A-A of FIG. 1;
[0039] FIG. 3 shows one preferred embodiment of the gas
jet-absorption apparatus used in the invention.
DETAILED DESCRIPTION OF THE INVENTION AND EMBODIMENTS
[0040] The jet-reactor of the present invention will be described
in detail with the accompanying drawings and embodiments, but not
limited to these embodiments and examples.
[0041] FIG. 1 shows a flow duct type jet reactor 1 of the
invention, comprising: an internal feed tube 3, an external feed
tube 4 coaxial with the internal feed tube 3, and an annular space
5 defined between the two feed tubes, wherein both ends of the
external feed tube are closed; a reaction tube 7 coaxially
connected to the downstream of the internal feed tube; jet holes 6
made in the wall of the downstream part of the internal feed tube 3
and the jet holes 6 are connected with flow ducts 8.
[0042] According to the reactor of the present invention, the
external feed tube 4 is engineered inside with porous plates,
baffle plates, or packing layers and the like to stabilize reactant
streams. There is no specific requirement on the space thickness of
the annular space 5, and the space thickness of the annular space 5
is usually 0.1 to 0.8 times of the inner diameter of the internal
feed tube, preferably 0.2 to 0.6 times and more preferably 0.2 to
0.4 times. A divergent channel can be understood as a channel with
its cross section gradually increasing along the stream flow
direction. The inner diameter D of the reaction tube 7 is larger
than the inner diameter of the internal feed tube 3, and generally
the inner diameter D of the reaction tube is 1 to 2 times of the
inner diameter of the internal feed tube, and preferably 1.1 to 1.5
times. The angle .alpha. between the divergent channel and the
stream flow direction in the internal feed tube is 10-30 degrees.
The number of jet holes 6 is 2-20, preferably 3-15, and more
preferably 3-10. The total cross sectional area of all of jet holes
6 or flow ducts 8 is 2-30% of that of the internal feed tube, and
preferably 5-15%.
[0043] FIG. 2 is an enlarged view of cross section along the line
A-A of FIG. 1. In one preferred embodiment, four flow ducts 8 are
arranged in the internal feed tube 3, and jet holes 6 are
symmetrically arranged on the same cross section over the internal
feed tube. The number of flow ducts is 4. The outlets of all of
flow ducts 8 are positioned at a first suppositional circle 9, and
the first suppositional circle is co-axial with the phosgene feed
tube. The diameter of the first suppositional circle 9 is 0.1 to
0.99 times of the inner diameter of the internal feed tube, and
preferably 0.4-0.9 times. The outlets of flow ducts 8 are
preferably symmetrically arranged on the first suppositional circle
9, and preferably on the same cross section. The flow ducts 8 are
engineered to be a curve shape, and the curve is overlapped with a
second suppositional circle 10 defined by the center of jet holes,
the center of outlets of flow ducts and the axis of the internal
tube. The instantaneous flow direction of the amine vapor at the
outlet of a single flow duct is preferred to be tangent with the
second suppositional circle 10. The proper arrangement of flow
ducts achieves that the amine streams from four flow duct outlets
form whirlpool under the direction effect and reinforce vortex so
as to make amines and phosgene mixed and react fast.
[0044] The phosgenation reaction is conducted in the
above-described reactor, the amine vapor diluted with an inert gas
or with an inert solvent vapor enters the external feed tube 4 via
its inlet 2, flows through the annular space 5 and jet holes 6 in
the wall of the internal feed tube 3 to flow ducts 8 and then is
ejected to the phosgene stream. The phosgene stream flows directly
through the internal feed tube 3 to the reactor 1. Under the
direction effect of flow ducts 8, several amine streams from flow
ducts 8 form whirlpool and reinforce vortex, and usually they are
mixed with phosgene in a strong turbulent flow state and then
enters a reaction tube 7 via a divergent channel with the reaction
continued to obtain a high temperature gas mixture of corresponding
isocyanates, phosgene and so on. The high temperature gas mixture
then flows into a gas jet-absorption apparatus for quenching and
absorption to obtain desired phosgenation solution.
[0045] Prior to the phosgenation reaction, the amine is generally
heated to 120.degree. C.-500.degree. C., and preferably 250.degree.
C.-400.degree. C., and the amine vapor is usually diluted with an
inert gas like nitrogen or argon or with an inert solvent vapor of
toluene, xylene, chlorobenzene, o-dichlorobenzene or decalin; the
phosgene is generally heated to 120.degree. C.-500.degree. C., and
preferably 250.degree. C.-400.degree. C. Based on the mole quantity
of amino group, phosgene exceeds 25%-350%, and preferably 50%-250%,
and the use amount of the inert gas or the inert solvent is usually
0.1-2 times of the mole of amino groups, and preferably 0.2-1
times.
[0046] During the phosgenation reaction, the pressure (absolute
pressure) in feed tubes is preferably 200 to 3000 mbar, and the
outlet pressure of the reaction tube of the reactor is preferably
150 to 1500 mbar. The velocity of phosgene prior to the mixing is
at least 1 m/s, and preferably 3-20 m/s; the velocity of the amine
vapor at the outlets of jet holes is usually 6-120 m/s, and
preferably 20-100 m/s.
[0047] FIG. 3 shows a preferred embodiment of the gas
jet-absorption apparatus used in the invention. After the
phosgenation in the reaction tube 7, the high temperature gas
mixture flows into a jet-absorption apparatus for quenching. An
absorption solution is pressured by a circulation pump 14, and then
ejected to the jet absorber via a nozzle of the jet absorber 12;
the high temperature gas mixture is rapidly sucked into the jet
absorber due to the negative pressure brought by the high speed
flow of the solution, so as to achieve sufficient mixing of the
solution and the gas mixture, and then quenching; the reaction
product in an absorption trough 13 is further collected and
absorbed by a liquid solvent. One part of the absorption solution
in the absorption trough is transmitted via the circulation pump 14
to a phosgenation solution post-process system 15 for solvent
removement and purification, another part is transmitted to the top
of a packing tower 19 to wash the gas in the absorption trough 13,
and the third part is transmitted to the jet absorber 12 for
quenching and absorption of the high temperature gas mixture with a
supplementing fresh solvent 16 together. The gas phase after going
through the packing washing layer is further condensed in a
condenser 18 (cooling medium is water), wherein partial solvent and
products in the gas phase flow into the condenser 18 at atmospheric
pressure, and incondensable gas is transmitted to a HCl and
COCl.sub.2 recycle device 17 so as to improve the post-treatment
efficiency of phosgenation solution.
Example 1
[0048] 4,4'-diaminodicyclohexylmethane (HMDA), phosgene and
nitrogen, in a mole ratio of 1:4:1, continuously flow to their
corresponding feed tubes respectively. The downstream part of the
reactor is connected with a gas jet absorption apparatus (for
quenching) and an absorption tower for excess phosgene and
hydrochloride. HMDA, phosgene and nitrogen are preheated to
360.degree. C. prior to entering the reactor shown in FIG. 1. The
HMDA vapor is diluted with an equivalent amount of nitrogen by the
mole of the HMDA to form a mixture, and then the mixture flows into
flow ducts via six lateral holes in the internal feed tube; the
inner diameters of lateral holes and flow ducts are 1.5 mm, the
inner diameter of the internal feed tube is 12 mm, the inner
diameter of the external feed tube is 30 mm, the inner diameter of
the annular space 5 is 20 mm, the distance between lateral holes
and the bottom of the annular space is 1 cm, the distance L from
lateral holes to the starting point of the divergent channel is 5
cm, the angel .alpha. between the divergent channel and the stream
flow direction in the internal feed tube is 20 degrees, and the
inner diameter D of the reaction tube is 15 mm. The instantaneous
flow direction of the amine vapor at the outlet of a single flow
duct is tangent with a second suppositional circle defined by the
center of jet holes, the center of outlets of flow ducts and the
axis of the phosgene feed tube, and the diameter of the first
suppositional circle is 0.65 times of the inner diameter of the
internal feed tube.
[0049] The vacuum in the reaction tube is maintained at -400 mbar
by the sucking effect of high speed liquid in the gas jet
absorption apparatus (a complex vacuum system and cost are saved).
Wherein, the velocity of the mixture of the amine vapor and
nitrogen through flow ducts is about 38 m/s, and the velocity of
phosgene prior to the mixing is about 8 m/s. After emerging from
the reaction tube of the reactor, the reaction product HMDI is
quenched to 140.degree. C. to 150.degree. C. by a gas jet
absorption apparatus with an o-dichlorobenzene solution of HMDI to
obtain a phosgenation solution, and the o-dichlorobenzene solution
is at 120.degree. C. The GC assay indicates that the content of
HMDI in the phosgenation solution is 99.24% (normalization), and
the yield of HMDI is 97.9% of the theory yield.
Comparative Example 1-1
[0050] Example 1 is repeated under the same conditions, but the
flow duct type jet reactor is replaced by a central nozzle type jet
comprising a central nozzle and an annular space wherein the cross
sectional area of the central nozzle equals to the total cross
sectional area of flow ducts, the area of the annular space between
the central nozzle and the wall of the cylindrical reactor equals
to the cross sectional area of the phosgene feed tube in Example 1
and the area of the reaction tube connected to the bottom of the
mixer equals to that of the reaction tube in Example 1. In this
central nozzle type reactor, a mixture of the amine vapor and
nitrogen flows through the central nozzle, and phosgene flows
through the annular space. The GC assay indicates that the content
of HMDI in the phosgenation solution is 99.08% (normalization), and
the yield of HMDI is 97.4% of the theory yield.
Comparative Example 1-2
[0051] The gas jet absorption apparatus is replaced by a solvent
absorption tower to quench the high temperature gas mixture (which
needs a complex vacuum system and an additional cooling system),
and the rest is the same as Example 1. The yield of HMDI is 97.6%
of the theory yield. It shows that the yield is relatively lower
and the system is more complex by comparison.
Example 2
[0052] 4,4'-diaminodicyclohexylmethane (HMDA), phosgene and
nitrogen, in a mole ratio of 1:4:1, continuously flow to their
corresponding feed tubes of the reactor shown in FIG. 1
respectively. HMDA, phosgene and nitrogen are preheated to
360.degree. C. prior to entering the reactor shown in FIG. 1. A
reactor similar to one in Example 1 is used, the HMDA vapor and
nitrogen flows into flow ducts via four lateral holes in the
internal feed tube; inner diameters of lateral holes and flow ducts
are 2.0 mm, the inner diameter of the internal feed tube is 12 mm,
the diameter of a first suppositional circle is 0.7 times of that
of the internal feed tube and the rest parameters are the same as
those in Example 1. The vacuum in the reaction tube is -400 mbar,
the velocity of the mixture of the amine vapor and nitrogen through
flow ducts is about 34 m/s, and the velocity of phosgene prior to
the mixing is about 8 m/s. After emerging from the reaction tube of
the reactor, the reaction product HMDI is quenched to 140.degree.
C. to 150.degree. C. by a gas jet absorption apparatus with an
o-dichlorobenzene solution of HMDI to obtain a phosgenation
solution, and the o-dichlorobenzene solution is at 120.degree. C.
The yield of HMDI is 97.8% of the theory yield.
Example 3
[0053] Isophoronediamine (IPDA), phosgene and nitrogen, in a mole
ratio of 1:4:1, continuously flow to the same reactor as one in
Example 1. Prior to entering the reactor, IPDA, phosgene and
nitrogen are separately preheated to 320.degree. C. Under nearly
the same reaction conditions, the yield of obtained IPDI is 98.8%
of the theory.
* * * * *